1. Field of the Invention
The present invention relates to a tray locking apparatus of a disc drive to lock a tray inserted into the disc drive and unlock the tray to be ejected.
2. Description of the Related Art
In a known disc drive using a disc as a recording medium, a tray to carry the disc into the disc drive is provided. That is, when the disc is placed on the tray and inserted into the disc drive, the disc is loaded at an installation position in the disc drive and then recording and/or reproduction is performed to/from the disc. Since the tray must not be ejected during recording and/or reproduction, a tray locking apparatus to lock the tray in the disc drive is provided.
FIG. 1 shows the structure of a tray locking apparatus disclosed in Japanese Patent Publication No. 2000-11513. As shown in FIG. 1, the tray locking apparatus includes a locking pin 35 provided in a main body 13 of a disc drive, a locking lever 50 installed at the lower surface of a tray 14 to be selectively locked by the locking pin 35, and a driving mechanism 60 to drive the locking lever 50.
The locking lever 50 includes an arm 51 installed to rotate around a rotation shaft 53 provided at the lower surface of the tray 14, on which a hook portion 51a coupled to the locking pin 35 is formed, and a lever 52 installed to rotate around the rotation shaft 53. As shown in FIG. 1, the arm 51 is elastically biased clockwise with respect to the lever 52, by a first spring 55 and the lever 52 is elastically biased clockwise with respect to the tray 14 by a second spring 56. Thus, the net result is that the locking lever 50 receives an elastic force in the direction in which the hook portion 51a is coupled to the locking pin 35.
Also, the driving mechanism 60 includes a plunger 63 supported by a yoke 62 and having one end coupled to a coupling pin 52e of the lever 52, a permanent magnet 64 attracting the other end of the plunger 63, and a coil 61 wound around the yoke 62 and applying an electrostatic force to the plunger 63.
When the tray 14 having a locking apparatus is inserted into the main body 13 of the disc drive, the hook portion 51a of the arm 51 is interfered with and pushed by the locking pin 35 and the arm 51 rotates counterclockwise, as shown in FIG. 2A. As the tray 14 continues to enter and is completely loaded at an installation position in the main body 13 of the disc drive, as shown in FIG. 2B, the arm 51 returns to the original position by an elastic force of the first spring 55 so that the hook portion 51a is caught by the locking pin 35. Thus, as the hook portion 51a is caught by the locking pin 35, the tray 14 is not ejected from the main body 13 of the disc drive. Here, since current flows such that an electromagnetic force in the opposite direction to an attracting force by the permanent magnet 64 can act on the plunger 63, the state in which the two forces are offset is maintained.
In the meantime, when the tray 14 is drawn from the main body 13, the direction of current flowing in the coil 61 is controlled so that an electromagnetic force acts on the plunger 63 in the same direction as the attracting force of the permanent magnet 64. Thus, the plunger 63 receiving the attracting force of the permanent magnet 64 and the electromagnetic force formed by the current flowing in the coil 61 moves toward the permanent magnet 64, as shown in FIG. 2C. Here, as the plunger 63 pulls the coupling pin 52e, the locking lever 50 is rotated counterclockwise. Accordingly, the hook portion 51a is unlocked from the locking pin 35 so that the tray 14 can be smoothly drawn from the main body 13.
Typically, a push unit (not shown) to apply an elastic force to force the tray 14 out of the main body 13 is installed in the main body 13. Thus, as soon as the locking is released, the push unit slightly pushes the tray 14 outside the main body 13. Then, a user is only needed to manually pull the tray 14 to draw it from the main body 13. When the locking is released so that the tray 14 is drawn, current is applied again to the coil 61 of the driving mechanism 60 so that an electromagnetic force acts on the plunger 63 in the direction opposite to the attracting force of the permanent magnet 64. Then, the two forces are offset so that the plunger 63 is in a free state. Here, the locking lever 50 returns to its original position by the elastic forces of the first and second springs 55 and 56, as shown in FIG. 2D.
However, in the tray locking apparatus having the above structure, current is continuously applied to the coil 61 to generate the electromagnetic force to compensate for the attracting force by the permanent magnet 64. Thus, a locking state in which the hook portion 51a of the locking lever 50 and the locking pin 35 are coupled is maintained, and electric power consumption increases. In view of the need for an energy saving apparatus, an improved apparatus capable of saving electric power is needed.